how do i make an image gradually disappear?

i dont mean fade out with the interpolate behavior. i need it to disappear from top to bottom as its self.time changes. keeping its same dimensions so not just shrinking its width until its zero. any help is appreciated.

Not sure what you want your clock to look like exactly but maybe check on YouTube: how to create a full circle timer gamesalad... Might at least give some ideas. There are also other videos for clocks in GS...